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OSCAR-11 Report




                OSCAR-11 REPORT   16 February 2004

OSCAR-11 was launched on 01 March 1984. After nearly 20 years in orbit,
it is still transmitting useful data.  To commemorate it's 20th birthday,
AMSAT-UK is issuing a special QSL for reports of reception during March.
There will be special endorsements for hearing the satellite on it's
birthday, and for mode-S reception.  For full details visit the AMSAT-UK
website at http://www.amsat-uk.org.uk/

Recently, ground control have been reloading the diary software. This
operation was successful.  However, the diary system still failed to work,
due to a suspected memory failure.

One consequence of these ground control operations, is that the mode-S
beacon was turned OFF for several days, and the watchdog timer sequence was
reset.   At the present time, the mode-S beacon is ON, and the VHF beacon
OFF.  I am expecting the VHF beacon to startup again around 19 February,
but ground control operations may change this date.

During March ground control are hoping to reset the timer each time the
VHF beacon switches OFF.  This should minimise the OFF time, but there
will be some gaps in the transmissions.

For the latest news, visit my website   http://users.zetnet.co.uk/clivew

During the period 25 January to 16 February 2004 the 145.826 MHz. beacon
has been heard transmitting continuous ASCII telemetry from 04 February to
07 February, but it may have been ON two or three days earlier. During
this period good signals have been received.

The internal temperatures have remained fairly constant. They are now
13.2C, 10.2C and 17.0C for battery, telemetry electronics and command
decoder, respectively. Solar eclipse predictions indicate that temperatures
are expected to increase, reaching a peak in March, a trough in June/July
and then increasing until the end of September, when the satellite will
encounter continuous sunlight for the remainder of the year. Higher
temperatures and greater temperature changes are expected this year,
compared to 2003.

The battery voltage observed during daylight passes has increased.
Observations have varied between 13.7 and 13.8 volts, with an average
value of 13.75 volts. The increase in voltage was caused by the reduction
of current due to the S-band beacon being OFF.

Spin periods of 327 to 380 seconds have been measured from the magnetometer
telemetry. The rotational speed is nominal and variations random. The
direction of rotation is normal.

Users of OSCAR-11 should note that the date in the telemetry is advanced by
three days.  The time is advanced by 19.3 minutes, and this error is
increasing by about one minute per year.

The mode-S beacon on 2401.5 MHz. has been heard by Ken W7KKE, Wilhelm
OE6AG, and Jack W9JIU. Ken reported signals one S-point above the noise.
He uses a
one metre offset dish, G3RUH patch, DEM pre-amp & Drake downconverter.
Wilhelm reported signals 25 dB above noise. He also reported the loss of
beacon signals between 28 January and 12 February. Jack received the beacon
at S8. He uses a Drake converter, and M2 pre-amp. Many thanks for all
those reports.

OSCAR-11 now operates in a default mode, controlled by the watch-dog timer.
The satellite transmits continuous ASCII telemetry for about 10 days on
145.826 MHz., followed by about 10 days of silence. This regular
sequence might be interrupted by ground control, especially during March,
when ground control will attempt to minimise OFF periods.

The mode-S beacon is ON continuously, even when the VHF beacon is
OFF, nominally transmitting an unmodulated carrier on 2401.5 MHz.
There is however a VERY low level of AFSK modulation, (now a constant
1200 Hz. audio tone), which has been detected on strong signals.
Telemetry indicates that the beacon has partially failed, and is
delivering half power.  This beacon is a useful test source for those
testing mode-S converters, as an alternative to OSCAR-40. However the
signals are very weak, and there is a lot of Doppler. Users should
also note that the polarisation of OSCAR-11 is LHC. Even if you can't
hear OSCAR-11, your equipment may still be OK for OSCAR-40. Any
reports of reception on 2401.5 MHz. would be most welcome.  Please
e-mail g3cwv@amsat.org.

The 435.025 MHz. beacon is normally OFF.  It can only be heard on the
very rare occassions when the satellite is being commanded by ground
control, ie. within range of Guildford, UK.  When the 435 MHz beacon is
transmitting, the 145 MHz beacon is normally OFF.  The data transmitted
is mainly binary.

Listeners to OSCAR-11 may be interested in visiting my web site.

The web site contains details about using a soundcard for data
capture, and also details about using hardware demodulators. There is
software for capturing data, and decoding ASCII telemetry.
There is an archive of raw data for analysis, which is continually
being expanded, as new data is captured.  Originally this was for
WOD, but it is now being expanded to include ASCII telemetry. At the
present time the telemetry covers 1996 to April 2003.  I will add
other years as time permits.  In parallel there is a news archive
which provides an overview of the state of the satellite, at the
times when the telemetry was captured.

If anyone out there can provide any data, particularly for the 1984
to 1993 years, this would be most appreciated.  Please e-mail me
with details.  However please DO NOT SEND ANY FILES, before futher
discussion.

Also included are some audio files, examples of each type of data
transmitted by OSCAR-11, each one plays for about ten seconds.  There
are also examples of mode-S reception.  All the audio files are
zipped, so that they can be played off-line.  These should help
listeners identify the various types of data, and give an indication
of the signal quality required for successful decoding.

The URL is -

      http://www.users.zetnet.co.uk/clivew/

If you place this bulletin on a terrestrial packet network, please
use the bulletin identifier $BID:U2RPT94.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org
----
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